This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-276419, Sep. 29, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a linear guide apparatus used in a head portion of an electronic component mounting machine, for example.
A linear guide apparatus is composed of a rail, bearing block, etc. A first raceway groove is formed on the outside face of the rail, while a second raceway groove is formed on the inside face of the bearing block. Rolling elements such as balls are held between the first and second raceway grooves. The rail and the bearing block can relatively move with smoothness with the aid of the rolling elements.
In the linear guide apparatus constructed in this manner, the bearing block is provided with a seal member such as an underseal, whereby dust or. other foreign substances are prevented from getting into the bearing block (onto the rolling contact surface of the rolling elements, in particular).
Seal means described in Jpn. Pat. Appln. KOKAI Publication No. 5-164128, for example, is provided with an underseal that is attached to the underside of a bearing block. A part of the underseal is sandwiched between the outside face of the rail and the inside face of the bearing block. In seal means described in Jpn. Pat. Appln. KOKAI Publication No. 5-223122, on the other hand, the outside face of a rail is formed having a groove that extends in the direction of movement of a bearing block. A part of a protector that is attached to the bearing block is fitted in the groove. Both these prior art examples use outside components, such as the underseal, protector, etc.
Thus fitted with the outside components, however, the conventional linear guide apparatus requires use of increased components and cannot be favorably reduced in size and weight. These days, in particular, there is an urgent demand for the reduction in size and weight of linear guide apparatuses, such as head portions of electronic component mounting machines, in order to shorten the mounting time. It is hard to meet the request for the small-sized lightweight apparatuses if outside components, such as an underseal, protector, etc., are attached to the bearing block or the like.
In order to reduce frictional force between the rail and the bearing block, it is not advisable to use an outside component, such as an underseal, which moves in contact with the rail. In some linear guide apparatuses that are used in a relatively clean working atmosphere, therefore, the bearing block is not provided with any outside component such as an underseal.
However, modern electronic components are becoming smaller and smaller or thinner. For example, a resistor-capacitor chip, the presently smallest chip, measures about 1.0 mm by 0.5 mm, and its thickness is reduced to about 0.3 mm. Chips measuring 0.6 mm by 0.3 mm and 0.2 mm thick are also being developed.
Even in a small-sized linear guide apparatus of the conventional type, the gap between the outside face of a rail and the inside face of a bearing block is 0.4 mm wide. If a conventional linear guide apparatus having no seal means is used in a head portion of a mounting machine that handles miniature components of the aforesaid type, therefore, foreign substances such as defective chips that are produced during mounting operation may possibly get into the gap between the rail and the bearing block. Foreign substances in the guide apparatus may damage or lock the bearing block. In consequence, the linear guide apparatus cannot fulfill its inherent durability and operating efficiency.
Accordingly, the object of the present invention is to provide a linear guide apparatus capable of preventing foreign substances from getting into the gap between a rail and a bearing block without using any outside component such as an underseal.
In order to achieve the above object, a linear guide apparatus according to the present invention comprises a rail having a ground outside face with first raceway groove thereon and a bearing block having an inside face and a base portion and movable in the longitudinal direction of the rail, the inside face having thereon second raceway groove opposed individually to the first raceway groove of the rail, a worked surface formed by grinding on that portion of the inside face of the bearing block which is situated between the second raceway groove and the base portion, and a labyrinth seal portion formed of the worked surface and the outside face of the rail and serving to prevent foreign substances from getting into the first and second raceway grooves.
According to the present invention, the linear guide apparatus capable of preventing invasion of foreign substances without the use of any outside component, such as an underseal, can be provided at low cost. Using no outside component, the linear guide apparatus of the invention can be reduced in size. According to the linear guide apparatus of the invention, foreign substances such as defective chips can be prevented from being caught between the rail and the bearing block, in a head portion of an electronic component mounting machine, for example. Thus, the linear guide apparatus can fulfill its inherent durability and high functional characteristics.
Preferably, in this invention, the outside face and the first raceway groove of the rail are ground simultaneously, and the worked surface and the second raceway groove of the bearing block are ground simultaneously. According to this invention, the labyrinth seal portion formed between the rail and the bearing block can be controlled with higher accuracy.
In order to enhance the labyrinth seal effect, moreover, a projection extending in the longitudinal direction of the rail may be formed on the worked surface of the bearing block so that the gap between the rail and the distal end of the projection is partially narrowed. In this arrangement, a curtain, such as sealed lubricating grease, can be formed with ease. Alternatively, a projection extending in the longitudinal direction of the rail and its mating recess may be formed on the worked surface of the bearing block and in the outside face of the rail, respectively, to enhance the labyrinth seal effect further.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.